The present invention relates to a method and apparatus for generating print data suitable for a laser printer which effects writing on an electrostatic photoconductor as a latent image by subjecting a laser beam to on-off modulation on the basis of data representing a character pattern as a bit map, and in which, after toner is electrostatically attracted to the latent image, the image is transferred to recording paper so as to print a character or an image.
A laser printer is capable of printing characters and images with very high resolution by increasing the modulation accuracy of a laser beam. For this purpose, it is necessary to compose image data to be printed in the form of a high-density bit map pattern. In order to output character data of such a high-density bit map pattern, much time and labor are involved in the preparation of the data, and a large-capacity storage device for storing the same is required. This disadvantageously entails an increased cost of the apparatus.
To overcome such a problem, U.S. Pat. No. 4,847,641 discloses a technique whereby character pattern data corresponding to a character code outputted from a host apparatus or the like is stored in a first-in first-out memory, a dot located at a position where printing is to be effected and a plurality of dots surrounding that dot are sampled from the first-in first-out memory, and the sampled bit map pattern is compared with pattern data for comparison, such as a multiplicity of templates or matching bit map data prepared in advance. If the sampled bit map pattern matches the pattern data for comparison, the sampled bit map pattern is replaced with a correction dot pattern allotted to the pattern data for comparison, and this correction dot pattern is outputted as print data.
According to this technique, since the bit map pattern data outputted from a character generator can be corrected as necessary, it is possible to print a character pattern having a smooth contour without increasing the storage capacity of the character data storage means.
However, since the bit map pattern itself which is stored in the first-in first-out memory is used as an object of pattern matching, the number of data for which pattern matching is to be effected increases. Hence, in order to complete the pattern matching calculation within a time period during which one dot is printed, a large-scale calculation circuit is disadvantageously required.